Wiktionary

1. yadda(Noun)

   One of a set of items which do not need to be specified; often used in conjunction with the catch phrase yadda yadda yadda.

2. yadda(Interjection)

   Used three times in a row, or in combination with other words, to indicate part of a sentence which would be annoying to include, or which is incomprehensible, or which is just unimportant.

   "In fact, the academic said, crime trends are influenced far more by demographics and social forces and yadda, yadda, yadda than by police work." - Andrew Karmen